Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations, it discloses the credit model (2 credits, charged only on a successful return, free when the site ranks for nothing), the US-only geographic scope, and the index refresh cadence ('every few weeks'). That is genuinely useful operational context; it stops short of explaining auth needs or exactly what fields `changes` carries.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense paragraph, front-loaded with the resource and scope before moving to output shape and cost. Every clause carries information, though the colon-heavy listing of output fields makes it slightly harder to scan than a short structured breakdown.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no parameters and no output schema, the description correctly shoulders the burden of explaining what comes back (targets, changes, their fields) plus cost and cadence. The main gap is the absence of when-to-use guidance against overlapping visibility/keyword siblings.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4. The description usefully spends its space on output semantics instead, naming the `targets` and `changes` keys and the sub-fields (page, monthly searches, difficulty), which partially compensates for the absence of an output schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific resource and scope: 'The Google searches this site ranks in the top 20 for (US)', and further splits the output into `targets` (ranks 4–20) and `changes`. This is far more specific than sibling names like `visibility` or `keyword_research` and lets an agent tell what the tool returns without opening anything.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives a follow-up action ('Lift one target per PR on the page that already ranks'), which implies the tool's role in a workflow, but never states when to prefer it over overlapping siblings such as `visibility`, `visibility_run`, or `keyword_research`. Usage is implied rather than routed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.